After unlocking Ember, you can learn to unlock Isobel. You should return to gonfalon Bay and drive directly West. Cross the River Bridge on the west side of the island and continue until you reach the brown debris on the map of Takashima. Here, you will find castle navire wayshrine. In the temple of the road, there is an NPC named Lord remarde devley. Talk to them to understand what happened to the castle navire. This interaction starts the "heart tournament" task.

By tracking this task and following the first map marker, you will find Isobel outside castle navire. Talk to her and she will provide more details about what happened in the castle. When you finish the task, she will join you, which may take about 30 minutes to an hour. At the end of the mission, Isabel was unlocked as a companion. As mentioned earlier, you can only have one partner active at a time, so you need to choose between ember and Isobel.

If you want to use one temporarily and then call the other, you can easily do it through the "Favorites" menu. Go to this menu from the inventory screen, then click the Allies tab, and then click companion. Here, you will be able to choose any companion you unlocked before joining your trip. Your previous traveling companions will be sent back to the menu for your new companions to join. This can also increase your chances of earning ESO gold.

Traveling with companions can make the trip to Takashima in the ancient scroll ol more enjoyable, so don't be afraid to use any Isobel.